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'April s, 1924. l. C. W. BURGER CONTACT DRUM AND METHOD OF MAKING THE SAME l Filed Deo. 14, 1921 Patented Apr. 8, 1924.

UNITED STATES PATENT OFFICE.

CLARENCE W. BURG-ER, OF WASHINGTON, DISTRICT OE COLUMBIA.

CONTACT DRUM AND METHOD OF MAKING THE SAME.

Application filed December 14,1921. Serial No. 522,424.

To all whom 'it may concern:

Be it known that I, CLARENCE W. BUR GER, a citizen of the United States, residing at iVashington, District of Columbia, have invented certain new and useful Improvements in Contact Drums and Methods of lVIaking the Same, of which the .following is a specification. i

This invention relates'to contact drums such as are adapted to cooperate with resilient ngers or brushes for-'the purpose of controlling electric circuits.-

In Patent No. 1,394,768, granted October 25, 1921, to J. E. Smith and myself, there is shown a somewhat similar contact drum, and an apparatus in which it may be advantageously employed. e

Although the present -invention may be considered as a specic improvement over theI above patent, and as especially designed for use in connection with automatic transmitters for teaching telegraphic codes, it will be understood that, in'ts broader aspects, the invention relates tocontact drums for any purpose whatsoever,I such, for eX- ample, as for controlling motors, flashing lelectric signs, etc.

The object of the invention is to provide a practical and effective method of manufacturing such drums more cheaply than has heretofore been possible, and to produce an article which will be strong, durable, eilicient and reliable in service.

To this end, I propose to build up 'a contact drum from a series of discs and spacing elements, with insulating material filling the space between the discs, and being dressed off to form a smooth cylindrical surface.

In order that the invention may be readily understood, reference is had to the accompanying drawing forming a1 part of this specication, and in which:

Fig. 1 is a side view of a contact drum constructed in accordance with the inven-` tion.

Fig. 2 is a central transverse section through the same.

Fig. 3 is a similar sectional view but illustrating the elements of the drum in their seglarated condition before being assembled, an

Fig. 4 is a fragmentary sectional view on an enlarged scale showing certain details of construction and illustrating the method of applying the insulating material.

Referring to the drawing in detail, my improved drum comprises a series of parallel metallic discs, the twooutside ones of which are designated as 1 and, 2 respectively. These outside discs are` preferably of the form shown in Fig. 1, that Vis to say, they are complete wheels having openings 3 formed through them.

Passing centrally through the discs 1 and 2 and rigidly secured thereto is a `hollow shaft 4 which is somewhat longer than the distance between the discs 1 and 2, and ,projects beyond the discl 1 as shown in Fig. 2. To the projecting lend of this hollow shaft 4 is secureda gear wheel 11 by means of which the drum is rotated. The two discs 1 and 2 are properly spaced at the center by means of a sleeve 5 surrounding the shaft 4, and the wheel 11 is spaced from the' disc 1 by means of a similar though shorter sleeve 10. v

The discs are also secured together and held inv assembled relationby means of hollow rivets 6, as clearly shown in the drawing, suc-h rivets being preferablylocated near the periphery of the discs as will hereinafter appear.

Located between the outside discs 1 and 2 is a series of intermediate annular elements 7, of the same outside diameter as the discs 1 and 2. These 'elements 7, so far as the operation vof the contact drum. is concerned, might be complete-discs similar to 1 and 2, but for the ysake of cheapness and lightness, the interior of these elements is cut away, thus leaving only comparatively narrow fiat rings, as clearly shown in Figs. 3 and 4. For the sake of simplicity, however, these annularelements will'be referred to throughout the specification and claims as discs, and it will be understood that this word is intended to include annular rings, as well as complete discs. y Y

lThe annular discs 7 above described, Vare provided with openings`7au corresponding in number and position to the hollow rivets 6., so that, when the parts are assembled,y these rivets pass through the elements 7 as wellas the discs 1 and 2. u v v f Located between the discs 1 and v2, and the annular elements or discs 7 themselves', are

`a series of spacing elements 9. `These are preferably in the form of wire rings of a diameter slightly greater than that of the circle on which the rivets 6 are set, so that these rings snugly encircle or embrace the rivets. When the parts are assembled as shown in Fig. 2, it will be seen from an inspection of F ig. 4, that annular grooves 8 :are formed between the several discs and that the spacing rings 9 constitute the bottom of such grooves.

It will be understood that the peripheries both of the discs l and 2 and also the annular discs` 7 are cut or shaped to form notches and teeth, the latter constituting the Contact points. lf the drum is employed as a telegraph transmitter, the general appearance of these teeth and notches is indicated in Fig. l, the teeth being designated at 1,2, and the notches at 13. As shown, these teeth and notches are of varying lengths so as to give rise to the familiar dots and dashes of a telegraph code. lf on the other hand the Contact drinn be designed for 'use as a motor controller, a sign flasher, or for other purposes, the peripheriesof the discs will be correspondingly varied, and it will be understood that by the term teeth7 as employed in the claims, I intend to include any projection or formation whatsoever carried by the peripheries of the discs, even though such projection should extend for a large portion of the circumference.

'Having assembled the discs and spacing rings, with the `grooves 8 between the discs, as shown at the right in Fig. fl, l next lill such grooves, as well as the spaces or notches between the teeth or projections, with plastic insulating material such as indicated at .r in Fig. el. The material which l prefer to employ is raw rubber. After having filled all of the grooves and notches with. this material, it is subjected to a hardening process, as by vulcanizing. After the insulating material is thus hardened or vulcanized, the drinn, having a more or less irregular surface as indicated in Fig. l, is placed in a lathe or the like and turneth the tool being adjusted so as to dress the periphery of the drinn to a true smooth cylindrical surface as indicated by the line g/-.a in Fig. 2, with the teeth or projections l2 extending through the insulating material and terminating flush with .such smooth cylindrical surface.

Since, as will be readily understood, the discs l, 2 and 7 can be readily punched from sheet metal, and easily assembled in the manner described, it will he seen that l have provided an exceptionally cheap and effective method. of forming` contact drums, and it will also be observed that the finished drinn has a smooth cylindrical siii- 'face, composed partly of insulating material and partly of metallic contacts, such drum having all the advantages of those heretofore constructed by more tedious and expensive methOds.

i.,fisacar lVhat I claim is:

l. A Contact drum comprising a plurality of parallel metallic discs having peripheral teeth, spacing rings between the discs, means for holding said rings and discs is assembled relation, said rings being of smaller diameter than said discs, whereby annular grooves are formed outside of said rings between said discs, and insulating material filling said grooves and the spaces between said teeth, and terminating flush with the ends of said teeth.

2. A cont-act drum comprising a series of conducting discs, conducting spacing elements between said discs, and means for holding said discs and spacing elements in assembled relation. y

3. A contact drum coinprising-aseries of conducting discs, conducting spacing elements between said discs, and hollow rivets for holding said discs and spacing elements in assembled relation.

l. A contact drinn comprising a series of assembled, parallel discs, spacing elements between said. discs, and a hollow shaft eX- tending centrally through said discs and secured to the two outer ones only, the intermediate discs being cut away at their centers so as not to engage said shaft.

5. A contact drinn comprising a pair of outer metallic discs and a plurality of .intermediate annular metallic plates, said discs and annular plates being assembled in spaced parallel relation to form a cylindrical structure having a hollow interior, the peripheries of said plates and discs being provided with teeth, forming contacts.

6. The method of making a Contact drinn which consists in assembling a series of vrietallic discs, each having teeth on its periplr ery, in parallel spaced relation, filling the spaces between the outer portions of said discs and between said teeth with plast-ic insulating material, hardening said ma.- terial, and finally dressing olf the periphery of the drum to ferm a smooth cylindrical surface, with the ends of said teeth terminating flush with such surface.

7. The method of making a contact drinn which consists in assembling a series of parallel metallic discs with a seiies of spacing rings of smaller diameter, the rings and discs being,` alternately arranged so that annular grooves between the discs are formed. the rings constituting the bottom of said grooves, filling such grooves with plastic insiilating-materiah hardening said material, and then dressing oli' the material to forni a smooth cylindrical surface with poi-tiens of the periphery of said discs projecting there through.

In testimony whereof l affix my signature.

CLARENCE w. .B'nnenn 

